a(n) = floor(log(n)).

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =2a(8) =2a(9) =2a(10) =2a(11) =2a(12) =2a(13) =2a(14) =2a(15) =2a(16) =2a(17) =2a(18) =2a(19) =2a(20) =3a(21) =3a(22) =3a(23) =3a(24) =3a(25) =3a(26) =3a(27) =3a(28) =3a(29) =3